Track rings for radial piston hydraulic pumps and motors



July 19, 1966 z. A. LOMNICKI 3,261,227

TRACK RINGS FOR RADIAL PISTON HYDRAULIC PUMPS AND MOTORS Filed Jan. 17. 1963 2 Sheets-Sheet 1 I l 75 r m 274;, *WW

July 19, 1966 2. A. LOMNlCKl 3,261,227

TRACK RINGS FOR RADIAL PISTON HYDRAULIC PUMPS AND MOTORS Filed Jan. 17. 1963 2 Sheets-Sheet 2 1 1.12:4. V/ZAu/u 1 477020 91 United States Patent 3,261,227 TRACK RINGS FOR RADIAL PISTON HYDRAULHI PUMPS AND MOTORS Zbigniew Alexander Lomnicki, Codsall, England, assignor to Bouiton Paul Aircraft Limited, Codsall, England Filed Jan. 17, 1963, Ser. No. 252,128 1 Claim. (Cl. 74567) The present invention relates to track rings for hydraulic pumps and motors of the radial piston type.

Pumps and motors of this type are known in which the rate of rotation and volume rate of flow are not strictly proportional, resulting in an irregular pump delivery or uneven motor torque, as the case may be, even when the pump is driven at a constant rate or the motor is supplied with liquid at constant pressure. Devices of this type are exemplified by Patents 1,477,300 and 1,526,343.

The present invention provides a track ring by means of which the volume rate of flow is uniformly proportional to the rate of rotation.

Accordingly the present invention provides a track ring for hydraulic pumps or motors of the radial piston type having five or more pistons, in which the transverse axial section of the running surface of the track ring is the locus of the end of a radial line rotating about the centre of the basic circle as defined below, the length of the line being C+f(A), where C is the radius of the basic circle and A is the angle between the radial line and the bisector of the angle subtended by the working sector as defined below, and in which (A) is defined by the followign conditions:

in which conditions R is the lift of the pistons, 2a is the angle subtended at the centre of the basic circle by the limits of the working sector, and 0c is defined by if n is even, where n is the number of pistons.

The cross-section of the running surface of the track ring of the present invention differs from a true circle, hereinafter called the basic circle by amounts which are functions of the angle A displaced by the respective point on the track ring at the centre of the basic circle.

The dwell sector is that sector of the basic circle between the limits of which and the working sector is the sector lying outside the dwell sector.

The formulae for f(A) hold true for i.e. over one semi-circle, and for the interval 1r 31r to 2 2 i.e. for the remaining semi-circle, (A) is defined as f(1r-A), thus becoming a mirror image of the function in the first semi-circle.

The formula given above refers to a pump (or a motor) with one stroke per revolution and n pistons (nZ-S). Motors (or pumps) with more than one, say S strokes per revolution and n pistons have also the required property provided that either (a) the two integers n and S have no common factor greater than unity, or

(b) n and S are both even numbers such that n/ 2 and 8/2 have no common factor greater than unity and 11/2 is an odd number greater than 3.

In the case of S strokes per revolution the track rings have to be contracted into S working sectors each S times smaller than the working sector in the case of one stroke per revolution. In other words a new track ring is defined in this case, by the formula C+g(A) where g(A) =f(SA) and f(A) is assumed to have a period of 21r. When A ranges from 0 to 211-, A/S ranges from 0 to 27r/S and, for S strokes per revolution, the same movements of the pistons relatively to the basic circle are repeated S times per revolution.

The track ring of the present invention has a contour such that the sum of the contributions of the pistons to the fluid delivery from the pump or to the motor per angular displacement is constant at each angular position.

A radial piston hydraulic pump with the present track ring will produce a constant rate of fluid flow when driven at a constant rate of rotation, The torque required to drive the pump will also be uniformly proportional to the pressure at which the fluid is delivered.

A radial piston hydraulic motor with the present track ring will produce a constant torque when supplied with fluid at a constant pressure. The volume rate of flow demanded by the motor will also be uniformly proportional to the rotational speed of the motor and vice versa for a pump.

The track ring design to produce the above features is dependent upon the number of pistons and upon the number of working sectors in one revolution of the pump 4 the rate of rotation control the pumping rate of the pump or the torque of the motor. If this can be achieved by a piston lift, R, over a working sector of one revolution,

then a pump or motor with two, three, or more working sectors per revolution and the same rate of rotation will produce the same pumping rate or torque, provided the piston lift is reduced proportionally i.e. R/ 2, R/ 3 etc.

The aforesaid designs have the additional property of producing piston accelerations as continuous functions and consequently providing relatively smooth operation: with pumps or motors having the numbers of strokes per revolution and of pistons satisfying conditions (b) (see above) a design can be achieved in which the resultant forces form a pure couple.

The improved track ring design can further be applied to variable delivery pumps and variable torque motors. The pistons of the pump or motor are to move around the interior of a tubular surface of which each cross-section perpendicular to the axis of the pump or motor corresponds with a track ring of the shape described. The maximum piston lift R is a function of the longitudinal position of the cross-section. By longitudinal displacement of the tubular surface along the rotary axis the pump delivery or motor torque can be varied in any desired manner.

The choice of the number of pistons is determined by the requirements of the pump or motor. The torque of of n, S and R and thus, for a given output torque, these items may be varied as desired provided that the final product is unaltered.

I claim:

A track ring to be used in combination with a radial piston machine having n pistons, said track ring having a cam surface in driving connection with each of said pistons and being shaped such that, assuming a motion of Of the following two tables, Table 1 gives the angles 5 each of said pistons around the center of said track ring of the working sectors and the dwell corresponding to the along a path determined by said cam surface thereof, a number of pistons of a pump or motor having one workpoint passing through the central longitudinal axis of ing sector per revolution, and Table 2 gives the radial each of said pistons would trace out an arcuate path which distances from the centre of the basic circle to the track may be considered to comprise an integral number S of ring f a pump or motor f hi h :5, R=1 unit and identical circumferential sections, where S is the number C=12 units. of strokes of each of said pistons per revolution of said Table 1 a 72 60 77.14 07.5 80 72 81. s2 75 83.08 77.14 84 78.75 a 18 a0 12. 86 22.5 10 18 8.18 15 0. 92 12.86 6 11.25

Table 2 pistons and track ring relative to each other, one half of each of said sections being a mirror image of the other Radial Radial half, and each of said section halves comprising three g g tgg gg g gg g i gs successive arcs subtending angles 6, 2a and 6 respectively KA) 0 IPA) 8 at the center of said track ring, the first and third of said Y arcs being circular arcs about said track ring center and (1000000 0000 110600 of radius (C-R) and (C+R) respectively, and the second 321 3 11.9168 8 2 3 2 IL 8343 of said arcs being a spiral arc of rad1us 32:22; 2:22 11 A 1 A 0' 402103 1214021 11: 5979 C +R |-sin L 0 475079 12. 4751 11.5249 a W a 8 23:12? 23:5 11:22 4 01669080 9691 1123309 35 about the center of said track ring, where: 8 tgg C is the radius of said spiral are at the midpoint thereof, 0.818310 12.8183 11.1817 R is the lift of said pistons and less than C, 3-

1 A is the angle subtended at the center of said ring by a 0.919080 12.9191 11.0809 radial lrne to sa1d m1dpo1nt of said sprral arc and a g-ggggg gggg 85g second radial line to another point of said spiral arc, 0 975079 12.9751 11. 0249 A ranging from u to +oc, 8 gggigg 33g; 86%? n is any integer not less than 5, 0. 990812 121 9908 11. 0032 a has any value determined by the equation 0 900052 12.9991 11.0009 2- 322221 022 11220 1: 000000 1310000 11: 0000 (n 1) 1 000000 13. 0000 11.0000 1 000000 13. 0000 11.0000 1. 000000 13. 0000 11.0000 when n 10 odd, and r 1. 000000 13. 0000 11. 0000 1 1. 000000 13. 0000 11. 0000 Sa=(1L-2)-% The meanings of the various terms used in the above when n is eve spec1ficat1on W1ll be explamed w1th reference to the acfactor greater i g fif gz g i g g zg gg gg i ggg v 9 P Y E dfavflngs, 1T1 Q S are both even 'numbers such that n/ 2 and S/ 2 have FIG. 1 1s a dragram showing the bas1c circle and the no common factor greater than un1ty, n/ 2 1s an odd track r1ng contour based thereon, and number greater than 3 FIG. 2 is a polar diagram of a track ring having the' measurements set out in Table 2. References Cited b the Exa In FIG. 1, the basic circle 1 is shown in full lines and y a rough derivation of the track ring contour 2 is shown 0 UNITED STATES PATENTS in broken lines. 1,477,300 12/ 1923 Thrift 1()3 174 This latter consists of two lobes, one inside and one 1,526,343 2/1925 Jouallfleaux 174 outside the basic circle. The lines 3 mark the boundaries 1,512,888 1/1927 Schneggenbllfgel' 103-161 between the working and dwell sectors. 3 934 Kraus 74--571 As shown, each Working sector subtends an angle of 20a 9 2/ 1937 B nedex 103-161 at the centre of the basic circle 1, having a radiu C. The 2,709,924 6/ 1955 'CaSteIIi 74568 distance from the centre of the basic circle to a point on 2,882,831 4/ 9' Da n vig 103161 a trick ring contour is a Cl-f(A). The angle subtended 3,046,950 7/ 96 mith lO3'-l74 t t :ectot: gseritsre of the bas1c circle by the l1m1ts of the dwell FOREIGN PATENTS FIG. 2-illustrates the shape of the track ring of which 336 1912 Great Britainthe measurements are set out in Table 2. This track ring is for a pump or motor having five p a piston 1i ft MILTON KAUFMAN, Primary Examiner. of one unit and a basic circle of twelve units, the working BROUGHTON DURHAM, Examiner- Sector subtendmg an angle of 1 W. s. RATLIFF, Assistant Examiner. 

